#include <stdio.h>
#include <string.h>

#include "iot_crc16.h"


/********** 1、 crc 检验 begin **********/

// crc校验
typedef union _CRC { 
    unsigned short crc16; 
    unsigned char bytes[2]; 
} CRC;  
static CRC crc;

// 校验函数
unsigned short CRC16(unsigned char *btyeArray, int len)  {
   //CRC crc; 
   crc.crc16 = 0xffff; 
   int i, l; 
   for (i=0; i<len; i++)  { 
       unsigned char ch = btyeArray[i]; 
       crc.bytes[0] = crc.bytes[0]^ch; 
       for (l=0; l<8; l++)  { 
           if (crc.bytes[0] & 0x01)  { 
               crc.crc16 = crc.crc16 >> 1; 
               crc.crc16 = crc.crc16 ^ 0xa001; 
           } 
           else  { 
               crc.crc16 = crc.crc16 >> 1;  
           } 
       } 
   }
   unsigned char swap = crc.bytes[0]; 
   crc.bytes[0] = crc.bytes[1]; 
   crc.bytes[1] = swap; 
   return crc.crc16; 
} 

/********** crc检验 end **********/
 

// 计算crc
unsigned short Cal_CRC16(unsigned char *pdata, int len)
{
    unsigned int i;
    unsigned short crc = 0xFFFF;
    
    while(len--)
    {
        crc ^= *pdata++;
        for (i = 0; i < 8; ++i)
        {
            if (crc & 1)
                crc = (crc >> 1) ^ 0xA001;
            else
                crc = (crc >> 1);
        }
    }
    
    return crc;
}

// crc校验：modbus
unsigned short CRC16_Modbus ( unsigned char *pdata, int len)
{
    unsigned short crc=0xFFFF;
    int i, j;
    for ( j=0; j<len;j++)
    {
        crc=crc^pdata[j];
        for ( i=0; i<8; i++)
        {
            if( ( crc&0x0001) >0)
            {
                crc=crc>>1;
                crc=crc^ 0xa001;
            }
        else
            crc=crc>>1;
        }
    }
    return crc;
}

/********** 2、 单字节校验和 begin ***********/

// 计算：单字节校验和，传入需要计算的字节，不包括校验位
unsigned char Cal_CheckSum(unsigned char *pdata, int len){
    unsigned char ret = 0; 
    int i; 
    for(i=0; i<len; i++)   
        ret += *(pdata++);
    return ret;
}

// 校验：单字节校验和，传入包括校验位在内的字节
// 返回：0为错误，1正确
int Check_CheckSum(unsigned char *pdata, int len){
    int ret = 0; 
    unsigned short cs = Cal_CheckSum(pdata, len-1);
	if(cs == pdata[len-1])
		ret = 1;
	return ret;
}

/********** 单字节校验和 end **********/ 


/********** 3、 厂家建议方法 ***********/

//CRC 高位字节值表：
static char auchCRCHi[] =
    {0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0,
     0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
     0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
     0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
     0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
     0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
     0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0,
     0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41,
     0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
     0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41,
     0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
     0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40,
     0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1,
     0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81, 0x40,
     0x01, 0xC0, 0x80,
     0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00,
     0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00, 0xC1, 0x81,
     0x40, 0x01, 0xC0, 0x80, 0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x00,
     0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40, 0x01, 0xC0, 0x80,
     0x41, 0x01, 0xC0, 0x80, 0x41, 0x00, 0xC1, 0x81, 0x40};

//CRC 低位字节值表：
static char auchCRCLo[] =
    {0x00, 0xC0, 0xC1, 0x01, 0xC3, 0x03,
     0x02, 0xC2, 0xC6, 0x06, 0x07, 0xC7, 0x05, 0xC5, 0xC4, 0x04, 0xCC, 0x0C, 0x0D, 0xCD,
     0x0F, 0xCF, 0xCE, 0x0E, 0x0A, 0xCA, 0xCB, 0x0B, 0xC9, 0x09, 0x08, 0xC8, 0xD8, 0x18,
     0x19, 0xD9, 0x1B, 0xDB, 0xDA, 0x1A, 0x1E, 0xDE, 0xDF, 0x1F, 0xDD, 0x1D, 0x1C, 0xDC,
     0x14, 0xD4, 0xD5, 0x15, 0xD7, 0x17, 0x16, 0xD6, 0xD2, 0x12, 0x13, 0xD3, 0x11, 0xD1,
     0xD0, 0x10, 0xF0, 0x30, 0x31, 0xF1, 0x33, 0xF3, 0xF2, 0x32, 0x36, 0xF6, 0xF7, 0x37,
     0xF5, 0x35, 0x34, 0xF4, 0x3C, 0xFC, 0xFD, 0x3D, 0xFF, 0x3F, 0x3E, 0xFE, 0xFA, 0x3A,
     0x3B, 0xFB, 0x39, 0xF9, 0xF8, 0x38, 0x28, 0xE8, 0xE9, 0x29, 0xEB, 0x2B, 0x2A, 0xEA,
     0xEE, 0x2E, 0x2F, 0xEF, 0x2D, 0xED, 0xEC, 0x2C, 0xE4, 0x24, 0x25, 0xE5, 0x27, 0xE7,
     0xE6, 0x26, 0x22, 0xE2, 0xE3, 0x23, 0xE1, 0x21, 0x20, 0xE0, 0xA0, 0x60, 0x61, 0xA1,
     0x63, 0xA3, 0xA2, 0x62, 0x66, 0xA6, 0xA7, 0x67, 0xA5, 0x65, 0x64, 0xA4, 0x6C, 0xAC,
     0xAD, 0x6D, 0xAF, 0x6F, 0x6E, 0xAE, 0xAA, 0x6A, 0x6B, 0xAB, 0x69, 0xA9, 0xA8, 0x68,
     0x78, 0xB8, 0xB9, 0x79, 0xBB, 0x7B, 0x7A, 0xBA, 0xBE, 0x7E, 0x7F, 0xBF, 0x7D, 0xBD,
     0xBC, 0x7C, 0xB4, 0x74, 0x75, 0xB5, 0x77, 0xB7, 0xB6, 0x76, 0x72, 0xB2, 0xB3, 0x73,
     0xB1, 0x71, 0x70, 0xB0, 0x50, 0x90, 0x91, 0x51, 0x93, 0x53, 0x52, 0x92, 0x96, 0x56,
     0x57, 0x97, 0x55, 0x95, 0x94, 0x54, 0x9C, 0x5C, 0x5D, 0x9D, 0x5F, 0x9F, 0x9E, 0x5E,
     0x5A, 0x9A, 0x9B, 0x5B, 0x99, 0x59, 0x58, 0x98, 0x88, 0x48, 0x49, 0x89, 0x4B, 0x8B,
     0x8A, 0x4A, 0x4E, 0x8E, 0x8F, 0x4F, 0x8D, 0x4D, 0x4C, 0x8C, 0x44, 0x84, 0x85, 0x45,
     0x87, 0x47, 0x46, 0x86, 0x82, 0x42, 0x43, 0x83, 0x41, 0x81, 0x80, 0x40};
 

// CRC 函数例程： 
// pushMsg 为需要校验的数组指针变量，usDataLen 为需要校验的数据个数变量
void MB_CRC16(char *pushMsg, unsigned short usDataLen) {
    char uchCRCHi=0xFF;     //高 CRC 字节初始化
    char uchCRCLo=0xFF;     //低 CRC 字节初始化
    unsigned int uIndex;    //CRC 循环中的索引
    while(usDataLen--)      //CRC 查表校验函数
    {
        uIndex = uchCRCHi ^ *pushMsg++;//计算 CRC
        uchCRCHi = uchCRCLo ^ auchCRCHi[uIndex];
        uchCRCLo = auchCRCLo[uIndex];
    }
    *pushMsg ++= uchCRCHi; //校验数据高位在后
    *pushMsg = uchCRCLo; //校验数据低位在前
}

/********** 其他方法 ***********/
// 可用
// write_cmd[7] = MB_CRC16(write_cmd, 7); // 0xCA;
// write_cmd[8] = MB_CRC16(write_cmd, 8); // 0x75;
unsigned char CRC16_OK(unsigned char *_pushMsg, unsigned char _usDataLen)
{
    unsigned char uchCRCHi = 0xFF;
    unsigned char uchCRCLo = 0xFF;
    unsigned char uIndex;
    while(_usDataLen--)
    {
        uIndex = uchCRCLo ^ *_pushMsg++;
        uchCRCLo = uchCRCHi^auchCRCHi[uIndex];
        uchCRCHi = auchCRCLo[uIndex];
    }
    return (uchCRCHi<<8|uchCRCLo);
}
